Offshore crane control based on adaptive external models

A novel controller for cranes employed in heavy-lift offshore marine operations is proposed. The control objective is to reduce the hydrodynamic slamming load acting on a payload at water-entry of moonpool operations while, at the same time, the values of the wire tension must be kept within acceptable bounds. The adopted solution relies upon the use of an adaptive observer and two external models; as a result, the closed loop system is adaptive with respect to both plant parameters and frequencies of the harmonic disturbances entering the system. Experimental results show improvements with respect to a previous internal model-based controller.